Polyaxial bone anchoring device and system including an instrument and a polyaxial bone anchoring device

ABSTRACT

A bone anchoring device includes a receiving part with a recess for receiving a rod and a flexible head receiving portion for pivotably holding a head of a bone anchoring element, a pressure member configured to exert pressure on the head when the head is held in the head receiving portion, and a clamping ring positionable around the head receiving portion and movable from a first position where the head is pivotable relative to the receiving part, to a second position where the clamping ring exerts a radial force on the head receiving portion to lock the head relative to the receiving part. When the clamping ring is at the first position, the clamping ring abuts the receiving part to restrict upward movement, while a surface of the clamping ring that faces upwards is exposed for engaging an instrument to move the clamping ring to the second position.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/930,043, filed Jul. 15, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/669,528, filed Aug. 4, 2017, now U.S. Pat. No.10,751,090, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/371,029, filed Aug. 4, 2016, and claims priorityfrom European Patent Application EP 16 182 818.1, filed Aug. 4, 2016,the contents of which are hereby incorporated by reference in theirentirety.

BACKGROUND Field

The invention relates to a polyaxial bone anchoring device and a systemincluding a polyaxial bone anchoring device and an instrument for usewith the device. More specifically, the bone anchoring device includes areceiving part for coupling a rod to a bone anchoring element, apressure member for exerting pressure onto a head of the bone anchoringelement and a clamping ring for locking the head and for releasing thelock, for example via the instrument.

Description of Related Art

U.S. Pat. No. 5,672,176 describes an anchoring member for connecting arod with a bone, including a screw member with a sphericalsegment-shaped head, a seat part receiving said screw head and said rod,and a pressure member formed to embrace said screw head. The seat parthas a portion tapering with a predetermined cone angle, and the pressuremember has an outer conical surface with a cone angle corresponding tosaid predetermined cone angle. The anchoring member can keep the screwhead of the screw member locked to the seat part when adjusting theposition of the seat part relative to the rod.

US 2013/0085536 A1 describes a polyaxial bone anchoring device includinga receiving part with a rod receiving portion and a head receivingportion for introducing and clamping of the head of a bone anchoringelement, and a locking ring configured to be arranged around the headreceiving portion. The locking ring includes an engagement structure forengagement with a tool to allow the locking ring to be moved out of thelocking position, for example, for releasing the locking mechanism. Thisenables a surgeon or other practitioner to carry out revisions orfurther positioning or re-positioning of the angular position of areceiving part with respect to the bone anchoring element.

US 2008/0108992 A1 describes a bone fixation device including a receiverhaving a deformable portion, a bone fastener having a head, the headbeing insertable into the receiver from the deformable portion, and aretaining member couplable to the deformable portion. The retainingmember deforms the deformable portion and angulatably retains thefastener relative to the receiver. The bone fixation device allows aquick loading of the bone fastener from a lower portion of the receiverand still maintains a high degree of angulation similar to thetop-loading bone fasteners.

U.S. Pat. No. 7,955,359 B2 describes a bone anchoring device includingan anchoring element having a head, a receiving portion for receivingthe head and for receiving a rod, a pressure element, and a closureelement that acts on the pressure element and on the rod toindependently fix the head in the receiving portion and fix the rod inthe recess of the receiving part.

SUMMARY

In spinal surgery, often multiple segments of the spinal column have tobe corrected and/or stabilized using a spinal rod and polyaxial boneanchoring devices. During such a procedure, repeated adjustments of boneanchoring elements and the rod relative to receiving parts of thepolyaxial bone anchoring devices may become necessary.

Embodiments of the invention provide a polyaxial bone anchoring devicethat allows for improved handling during surgery, and provides aninstrument adapted for use with such a polyaxial bone anchoring device.

According to an embodiment, the bone anchoring element can be lockedrelative to the receiving part at a certain angular position andreleased again independently from a fixation of the rod. The locking andreleasing of the bone anchoring element during surgery using theinstrument can also be carried out independently from use of a fixationelement, such as a fixation screw, that is used to finally lock the boneanchoring device.

According to one embodiment, the instrument can be used when the rod andthe fixation element are already inserted into a channel of thereceiving part, but when the rod is not yet fixed. Thus, a temporarylocking of the bone anchoring element in the receiving part can beeffected with the instrument. As a result, the polyaxial bone anchoringdevice allows a user to adjust or re-adjust an angular position of thereceiving part relative to the bone anchoring element several timeswhile the rod is already inserted.

In the same manner, the rod can be fixed and released independently oflocking of the head of the bone anchoring element relative to thereceiving part. Therefore, the polyaxial bone anchoring device accordingto an embodiment may exhibit the same or similar function as amono-axial bone anchoring device, wherein the axis of the shank of thebone anchoring element is fixed with respect to the receiving part. Inone embodiment, the polyaxial bone anchoring device may also exhibit thesame or similar function as a polyaxial bone anchoring device with apressure member and a two-part locking element, wherein the head and therod can be locked independently.

When the head of the bone anchoring element is locked in the receivingpart and the rod is still moveable, it is possible to pull the boneanchoring device with the instrument towards the inserted rod, andthereby also pull the associated vertebrae towards the rod forcorrecting a position of the vertebrae. With the polyaxial boneanchoring device and the instrument according to an embodiment, variousadjustments and re-adjustments of angular position and/or rod positionare possible during surgery, without applying large forces that couldresult in damage to surrounding material, such as tissue, blood vessels,or nerves. Revisions or secondary adjustments of the rod and thereceiving part can thus be performed in a more controlled manner.

The polyaxial bone anchoring device according to an embodiment permitsinsertion of the bone anchoring element first in the bone, andthereafter mounting the receiving part with the clamping ring onto thehead of the bone anchoring element. Moreover, with a polyaxial boneanchoring device according to embodiments of the invention, a modularsystem can be provided that allows for combining of various anchoringelements with the receiving part on demand, depending on the actualclinical requirements. This reduces the overall costs of using polyaxialscrews, reduces inventory, and gives the surgeon a wider or moreversatile choice of implants.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparentfrom the description of embodiments by means of the accompanyingdrawings. In the drawings:

FIG. 1 shows an exploded perspective view of an embodiment of apolyaxial bone anchoring device.

FIG. 2 shows a perspective view of the polyaxial bone anchoring deviceof FIG. 1 in an as-assembled state.

FIG. 3 shows a further perspective view of the polyaxial bone anchoringdevice of FIG. 1 in an assembled state.

FIG. 4 shows an enlarged cross-sectional view of the polyaxial boneanchoring device of FIGS. 1 to 3 , wherein the cross-section has beentaken in a plane perpendicular to an axis of an inserted rod andextending through the center of a receiving part of the bone anchoringdevice.

FIG. 5 shows a perspective view from the side of the receiving part ofthe polyaxial bone anchoring device of FIGS. 1 to 4 .

FIG. 6 shows perspective view from the bottom of the receiving part ofFIG. 5 .

FIG. 7 shows a top view of the receiving part of FIGS. 5 and 6 .

FIG. 8 shows a cross-sectional view of the receiving part of FIGS. 5 to7 , the cross-section taken along line A-A in FIG. 7 .

FIG. 9 shows a perspective view of a clamping ring of the polyaxial boneanchoring device of FIGS. 1 to 4 .

FIG. 10 shows a perspective view from the bottom of the clamping ring ofFIG. 9 .

FIG. 11 shows a top view of the clamping ring of FIGS. 9 and 10 .

FIG. 12 shows a cross-sectional view of the clamping ring of FIGS. 9 to11 , the cross-section taken along line B-B in FIG. 11 .

FIG. 13 shows a perspective view from the top of a pressure member ofthe polyaxial bone anchoring device of FIGS. 1 to 4 .

FIG. 14 shows a perspective view from the bottom of the pressure memberof FIG. 13 .

FIG. 15 shows a top view of the pressure member of FIGS. 13 and 14 .

FIG. 16 shows a cross-sectional view of the pressure member of FIGS. 13to 15 , the cross-section taken along line D-D in FIG. 15 .

FIGS. 17 a to 17 d show cross-sectional views of steps of mounting thereceiving part of the polyaxial bone anchoring device to an anchoringelement.

FIGS. 18 a to 18 c show steps of attaching an instrument to thepolyaxial bone anchoring device of FIGS. 1 to 4 according to anembodiment of the invention.

FIG. 19 a shows a cross-sectional view of the polyaxial bone anchoringdevice with the instrument of FIGS. 18 a to 18 c attached thereto,wherein the clamping ring assumes a first position, and wherein thecross-section is taken in a plane extending through the center of thereceiving part and positioned at an angle of about 45° relative to anaxis of an inserted rod.

FIG. 19 b shows an enlarged view of a detail of FIG. 19 a

FIG. 20 a shows a cross-sectional view of the polyaxial bone anchoringdevice with the instrument of FIGS. 18 a to 18 c attached thereto,wherein the clamping ring assumes a second position, and wherein thecross-section is taken in a plane extending through the center of thereceiving part and positioned at an angle of about 45° relative to anaxis of an inserted rod.

FIG. 20 b shows an enlarged view of a detail of FIG. 20 a.

FIG. 21 a and FIG. 21 b show steps of use of the polyaxial boneanchoring device with the instrument according to an embodiment of theinvention.

FIG. 22 shows a perspective view of a front portion of an instrumentaccording to another embodiment.

FIG. 23 shows a cross-sectional view of another embodiment of thepolyaxial bone anchoring device together with the instrument of FIG. 22.

FIG. 24 shows a perspective view of a front portion of a still furtherembodiment of the instrument.

DETAILED DESCRIPTION

As shown in FIGS. 1 to 4 , a bone anchoring device according to anembodiment of the invention includes a bone anchoring element 1 in theform of, for example, a bone screw having a shank 2 with a threadedportion and a head 3 with a spherically-shaped outer surface portion.The head 3 may have a recess 4 for engagement with a driver or tool. Thebone anchoring device also includes a receiving part 5 for receiving arod 6 to be connected to the bone anchoring element 1. Further, apressure member 7 may be provided in the receiving part 5 for exertingpressure onto the head 3 of the bone anchoring element 1. In addition,the bone anchoring device includes a clamping ring 8 that is mountableto the receiving part 5 for compressing a portion of the receiving part5, to exert pressure onto the pressure member 7 and in turn onto thehead 3. Lastly, the bone anchoring device also includes a fixationelement 9 in the form of, for example, an inner screw or set screw forfixing the rod 6 in the receiving part 5.

The receiving part 5 will now be described in greater detail, referringadditionally to FIGS. 4 to 8 . The receiving part 5 includes first end 5a and an opposite second end 5 b, and a central axis C that passesthrough the first end 5 a and the second end 5 b. The first end 5 a mayserve as an abutment for a portion of the instrument, as described ingreater detail below. A passage 51 extends through the receiving part 5from the first end 5 a to the second end 5 b. The passage 51 may beformed as a cylindrical coaxial bore 51 a in a region from the first end5 a to a distance from the first end 5 a, and may widen into anaccommodation space 51 b with a maximum inner diameter that is greaterthan an inner diameter of the coaxial bore 51 a. The accommodation space51 b serves for accommodating head 3 of the bone anchoring element 1 andat least a portion of the pressure member 7. After the section with themaximum inner diameter, the accommodation space 51 b narrows in anarrowing portion 51 c towards the second end 5 b. The narrowing portion51 c can be tapered, more specifically conically tapered, or can narrowin another manner. A substantially U-shaped recess 52 extends from thefirst end 5 a in direction of the second end 5 b, wherein a width of therecess 52 is slightly larger than a diameter of the rod 6, such that therod 6 can be placed in the recess 52 and can be guided therein. Therecess 52 forms a channel for the rod 6. By means of the recess 52, twofree legs 52 a, 52 b are formed, on which an internal thread 53 may beprovided. The internal thread 53 can be, for example, a metric thread, aflat thread, a negative angle-thread, a saw-tooth thread or any otherthread form. Meanwhile, the fixation element 9 in the form of an innerscrew has a thread corresponding to the internal thread 53 provided onthe legs 52 a, 52 b. Preferably, a thread form such as a flat thread ora negative angle thread is used to prevent or reduce splaying of thelegs 52 a, 52 b when the fixation element 9 is screwed-in.

At a distance from the first end 5 a, a circumferential groove 5 c isprovided that permits breaking off of a portion of the legs 52 a, 52 babove the groove 5 c. Hence, the upper portions of the legs 52 a, 52 bform extended tabs. The depth of the recess 52 is such that when the rod6 is placed into the recess 52 and the fixation element 9 is screwedbetween the legs 52 a, 52 b, the fixation element 9 does notsubstantially protrude out the receiving part 5 after the extended tabshave been broken off.

An upper part 50 of the receiving part 5 which is adjacent to the firstend 5 a has a substantially cylindrical outer surface. At an outersurface of the upper part 50 of the receiving part 5, an engagementstructure for engagement with the instrument is provided, wherein theengagement structure may be formed by a plurality of circumferentialribs 54 a, 54 b. In the embodiment shown, on each leg 52 a, 52 b, tworibs 54 a, 54 b are respectively provided. The ribs 54 a, 54 b arepositioned between the groove 5 c and a lower end 50 a of the upper part50. Each of the plurality of ribs 54 a, 54 b extends over a segment ofthe circumference of the upper part 50, for example, for approximately aquarter circle (see FIGS. 5 and 7 ). The arrangement is such that oneend of each rib 54 a, 54 b is positioned at the recess 52 and the otherend of each rib extends approximately to the middle of each leg 52 a, 52b. Hence, in a circumferential direction, there is a rib-free surfaceportion 55 a, 55 b on the outer surface of each leg 52 a, 52 b.Furthermore, the ribs 54 a, 54 b are arranged in an asymmetric mannerwith respect to a plane extending through the central axis C and alongitudinal axis L of the recess 52. More specifically, the positionsof the ribs 54 a, 54 b are offset from one another by 180° measured inrelation to the central axis C, and are rotated with respect to thecentral axis C such that the ribs 54 a of the leg 52 a extend to the rodreceiving recess 52 at one side of the receiving part 5 and the ribs 54b extend to the rod receiving recess 52 at the other side of thereceiving part 5. This permits the instrument to be placed first ontothe rib-free portions 55 a, 55 b, and then to be rotated to engage theribs 54 a, 54 b, as described in greater detail below. The ribs 54 a, 54b may have a substantially rectangular cross-section and may haveinclined end portions in the circumferential direction. It shall beunderstood that the number of ribs on each leg 52 a, 52 b is not limitedto two, and that one single rib or more than two ribs may instead beprovided on each leg in other embodiments. Also the shape of the ribsmay be different in other embodiments.

As shown in more detail in FIGS. 4 and 8 , on the inner wall of thepassage 51 in the upper part 50, two stops are provided for the pressuremember 7. A first stop is formed by the last thread turn of the internalthread 53, above an undercut 59 a positioned at the lower end of thethread 53. The first stop prevents upward movement of the pressuremember 7 when the head 3 is inserted into the receiving part 5. A secondstop is formed by a circumferential groove 59 b that is positioned at adistance from the first stop in a direction toward the lower end 50 a.The second stop prevents upward movement of the pressure member 7 whenthe pressure member 7 is at a lower position.

At the lower end 50 a of the upper part 50 of the receiving part 5, tworecesses 56 open towards the lower end 50 a and are positioned in acircumferential direction at approximately 90° from the center of theU-shaped recess 52. The recesses 56 have a small width in thecircumferential direction, and may have substantially straight sidewallsand a curved closed end. The recesses 56 serve for engagement withcorresponding projections of the clamping ring 8.

Between the upper part 50 and the second end 5 b, a head receivingportion 57 of the receiving part 5 is provided. The head receivingportion 57 has a substantially cylindrical outer surface, with a smallerdiameter than the diameter of the upper part 50 of the receiving part 5.Adjacent the second end 5 b, there is a portion 57 a of the outersurface that slightly tapers outwards. The head receiving portion 57includes the accommodation space 51 b. To allow insertion of the head 3,the head receiving portion 57 is flexible. In the embodiment shown, thehead receiving portion 57 includes a plurality of flexible wall sections57 b that are separated by slits 58 that extend in a longitudinaldirection and that are open towards the second end 5 b. The number andsize of the slits 58 is provided depending on the desired flexibility ofthe head receiving portion 57. An inner diameter of the passage 51 atthe second end 5 b is such that the head 3 can be inserted from thesecond end 5 b. The inner diameter of the passage 51 at the second end 5b may be slightly smaller than a greatest outer diameter of the head 3,so that the head receiving portion 57 may be expanded slightly when thehead 3 is inserted.

The clamping ring 8 will now be described in greater detail, referringadditionally to FIGS. 9 to 12 . The clamping ring 8 includes an upperend or first end 8 a and an opposite lower end or second end 8 b, andmay have a substantially cylindrical outer surface 81. The outerdiameter of the cylindrical surface 81 may be such that when theclamping ring 8 is mounted around the head receiving portion 57 of thereceiving part 5, the outer cylindrical surface 81 of the clamping ring8 and the outer cylindrical surface of the upper part 50 of thereceiving part 5 are flush with each other as depicted, for example, inFIGS. 2 to 4 . An inner diameter of the clamping ring 8 is such that theclamping ring 8 can be mounted around the head receiving portion 57,wherein the upper end 8 a faces towards the lower end 50 a of the upperpart 50 of the receiving part 5. Alignment features in the form of flatportions 82 are provided at the outer surface 81 of the clamping ring 8.The flat portions 82 are offset by 180° and may have a substantiallyrectangular contour. The alignment features provide a reference foraligning the clamping ring 8 correctly with respect to the receivingpart 5, in particular with respect to the ribs 54 a, 54 b.

The clamping ring 8 further includes on its outer surface 81 anengagement structure for engagement with the instrument. The engagementstructure includes a plurality of ribs 83 a, 83 b that are arranged onthe outer surface 81 of the clamping ring 8. The ribs 83 a, 83 b extendover a segment of an outer circumference of the clamping ring 8, forexample, for approximately a quarter circle or less than a quartercircle. In the embodiment shown, the ribs include two pairs 83 a, 83 bof ribs that are arranged diametrically opposite to one another. Eachpair 83 a, 83 b includes two axially spaced apart ribs extending in acircumferential direction on each side of the clamping ring 8. Theposition of the ribs 83 a, 83 b in a circumferential directioncorresponds to the position of the ribs 54 a, 54 b of the receiving part5 when the clamping ring 8 is mounted around the head receiving portion57 and when the flat portions 82 of the clamping ring 8 are aligned withthe U-shaped recess 52 of the receiving part 5. In other words, onegroup of ribs 83 a extends circumferentially around the clamping ring 8,from a circumferential position substantially adjacent to one flatportion 82 to a certain distance therefrom, and the opposite group ofribs 83 b extends circumferentially from a position substantiallyadjacent to the opposite flat portion 82 to a certain distancetherefrom. By means of this, rib-free surfaces 84 a, 84 b are formedbetween the ribs 83 a, 83 b that are aligned with the rib-free surfaces55 a, 55 b of the receiving part 5 when the clamping ring 8 is mountedaround the head receiving portion 57. The ribs 83 a, 83 b may havesubstantially rectangular cross-sections and inclined end portions in acircumferential direction. It shall be noted, however, that the shape ofthe ribs may be different in other embodiments. Also, in otherembodiments, there may be one single rib or more than two ribs on eachside of the clamping ring 8.

At the upper end 8 a, two opposite projections 85 are provided thatproject upward from the upper end 8 a towards upper part 50 of thereceiving part 5 when the clamping ring 8 is mounted to the receivingpart 5. The projections 85 have a shape that substantially fits into therecesses 56 at the lower end of the upper part 50 of the receiving part5. As depicted in FIGS. 2 and 3 , the projections 85 are atcircumferential positions substantially at the respective end of theribs that are farther away from the flat portions 82. The projections 85may have such a height that the clamping ring 8 is secured againstrotation around the receiving part 5 in both its upper and lower axialpositions.

As can be seen in particular in FIGS. 9 to 12 , clamping ring 8 furtherhas a first inner cylindrical surface portion 86 that is adjacent orsubstantially adjacent to the upper end 8 a. There may be a smallinclined surface or beveled surface 86 a provided adjacent to the upperend 8 a to facilitate mounting of the clamping ring 8 to the receivingpart 5. Adjacent or substantially adjacent to the lower end 8 b, aninner surface 87 of the clamping ring 8 may be tapered in a manner suchthat the inner diameter conically widens towards the lower end 8 b. Theinner surface 87 is configured to cooperate with the outer surfaceportion 57 a of the head receiving portion 57 in a manner such that whenthe clamping ring 8 is moved towards a lowermost position on the headreceiving portion 57, the cooperating surfaces 57 a of the headreceiving portion 57 and 87 of the clamping ring 8 exert an increasinginwardly directed radial force towards the pressure member 7 and thehead 3. Moreover, a height of the clamping ring 8 in an axial direction,as can be seen in FIGS. 2 and 3 , corresponds substantially to a heightof the head receiving portion 57 of the receiving part 5.

The pressure member 7 will now be described in greater detail, byreferring additionally to FIGS. 13 to 16 . The pressure member 7includes an upper or first portion 71 with an upper end 7 a and a loweror second portion 72 with a lower end 7 b. The second portion 72 has ahollow interior 73 that may be substantially spherically-shaped to clampthe spherical head 3 therein. The flexible portion 72 is open at thesecond end 7 b. A plurality of slits 74 extend from the lower end 7 bthrough the second portion 72. The number and dimensions of the slits 74are such that the wall of the second portion 72 is flexible enough tosnap onto the head 3 when the head 3 is being inserted into the hollowinterior 73. An outer surface portion 75 adjacent to the lower end 7 bof the pressure member 7 may be tapered, in particular conicallytapered. The outer surface portion 75 is configured to cooperate withthe inner surface portion 51 c of the receiving part 5 that is providedadjacent to the lower end 5 b of the receiving part 5. It shall beunderstood that in other embodiments, the outer surface portion 75 maynarrow in another manner towards the lower end 7 b. Another outersurface portion 76 of the second portion 72 of the pressure member maybe spherical segment-shaped as shown in the embodiment, so that thesecond portion is cap-like. It shall be noted that in other embodiments,the outer surface can have any other shape, such as tapered orcylindrical or combinations of tapered, cylindrical and spherical.

The first portion 71 of the pressure member 7 may have a substantiallycylindrical outer surface 77 adjacent to the second portion 72. In theembodiment shown, the second portion 72 is recessed with respect to thecylindrical portion 77. In other embodiments, however, any other shapemay be possible for the portion 77. A rod support surface 78 may beprovided in the first portion 71 that is configured to support aninserted rod 6. The rod support surface 78 may have a V-shapedcross-section in a direction transverse to the central axis C to permitsupport of rods of different diameter, but can also be flat orcylindrical or otherwise shaped.

The longitudinal axis of the rod support surface 78 extends transverseto the central axis C. To the left and to the right of the rod supportsurface 78, upstanding legs 79 a, 79 b are formed that have asubstantially flat inner surface and a substantially cylindrical outersurface. The upstanding legs 79 a, 79 b have outwardly directed portions700 a, 700 b at their free ends, respectively. The outwardly directedportions 700 a, 700 b are configured to engage the grooves 59 a, 59 bwhen the pressure member is in an insertion position and in a clampingposition of the head 3, respectively. Between the rod support surface 78and the upstanding legs 79 a, 79 b, grooves 701 a, 701 b extendingparallel to the rod support surface 78 are formed that render theupstanding legs 79 a, 79 b more flexible. The grooves 701 a, 701 b mayhave a circular segment-shaped cross-section. At the center of theupstanding legs 79 a, 79 b, elongate through-holes 702 a, 702 b may beprovided, the longitudinal axes of which are parallel to the centralaxis C. The through-holes 702 a, 702 b may be adapted to be engaged bypins (not shown) or other holding means to hold the pressure member 7inside the receiving part 5. To allow access to the head 3 with a driveror tool, a coaxial bore 702 is provided in the pressure member 7.

The dimensions of the pressure member 7 are such that the second portion72 can expand in the accommodation space 51 b when the head 3 of thebone anchoring element 1 is inserted therein. An outer diameter of thecylindrical portion 77 is slightly smaller than an inner diameter of thepassage 51 in the upper part 50 of the receiving part such that thepressure member 7 can slide therein. The pressure member 7 may beinsertable from the upper end 5 a of the receiving part 5, wherebyduring insertion the flexible second portion 72 may be slightlycompressed and the upstanding legs 79 a, 79 b may also be slightlycompressed towards each other until the second portion 72 is arranged inthe accommodation space 51 b and the outwardly directed portions 700 a,700 b engage the groove 59 a in the receiving part 5.

The receiving part 5, the pressure member 7, the clamping ring 8, andthe bone anchoring element 1, as well as the rod 6, may each be made ofbio-compatible materials, for example, of titanium or stainless steel,of a bio-compatible alloy, such as NiTi-alloys, for example Nitinol, ofmagnesium or magnesium alloys, or from a bio-compatible plasticmaterial, such as, for example, polyether ether ketone (PEEK) orpoly-l-lactide acid (PLLA). In addition, the parts can be made of thesame material, or can be made of different materials from one another.

Turning now to FIGS. 17 a to 17 d , a use of the polyaxial boneanchoring device will be explained. First, as illustrated in FIG. 17 a ,the bone anchoring element 1 may already be inserted into a bone 500before the receiving part 5 with the pressure member 7 and the clampingring 8 is mounted thereon. The pressure member 7 is in the receivingpart 5 in an insertion position where the head 3 can be inserted. Theoutwardly directed portions 700 a, 700 b extend into the first groove 59a at the receiving part 5, such that the last turn of the internalthread 53 forms a stop for the pressure member 7. The second portion 72of the pressure member 7 extends substantially into the accommodationspace 51 b. The clamping ring 8 is in an upper position in which theprojections 85 engage the recesses 56 and the upper end 8 a abutsagainst the lower end 50 a of the upper part 50 of the receiving part 5.Thus, the clamping ring 8 is correctly aligned and secured againstrotation relative to the receiving part 5.

As further illustrated in FIG. 17 b , the head 3 of the bone anchoringelement enters the head receiving portion 57 of the receiving part 5through the passage at the lower end 5 b. The receiving part 5 is thenfurther moved down, as can be seen in FIG. 17 c . Simultaneously, thehead 3 enters the hollow interior 73 of the second portion 72 of thepressure member 7. The pressure member 7 is prevented from escapingthrough the first end 5 a of the receiving part 5 by the stop providedby the last turn of the internal thread 53. Since the second portion 72of the pressure member 7 is flexible, it can expand in the accommodationspace 51 b when the head 3 is inserted, and snaps over the head 3.

Finally, as depicted in FIG. 17 d , the receiving part 5 is pulledupward with respect to the bone anchoring element 1 and the pressuremember 7. Thereby, the upstanding legs 79 a, 79 b snap with theiroutwardly directed portions 700 a, 700 b into the groove 59 b. At thesame time, the head 3 and the pressure member 7 are pulled into thenarrowing portion 51 c of the receiving part. The inner surface 51 c andthe outer surface of the pressure member 7 generate an increasingpressure onto the head 3. This frictional clamping of the head 3 in thereceiving part 5 may be such that the head 3 can be pivoted in thereceiving part 5 by overcoming the frictional force. Depending on thestrength of the frictional force, the receiving part may be temporarilyheld at a specific angular position relative to the bone anchoringelement 1. At the same time, the head 3 is prevented from being pulledout of the receiving part 5.

Turning now to FIGS. 18 a to 18 c , first, an instrument that is adaptedfor use with the polyaxial bone anchoring device will be described. Theinstrument 100 includes an outer tube 110 and an inner tube 120, whereinthe outer tube 110 and the inner tube 120 are axially displaceablerelative to each other along a longitudinal axis of the tubes. The outertube 110 and the inner tube 120 may be secured against rotation relativeto each other, so that rotating the outer tube 110 also rotates theinner tube 120 and vice-versa. The axial position of the inner tube 110relative to the outer tube 120 may be locked. The displacement of theinner tube 110 and the outer tube 120 relative to each other may beeffected, for example, by a lever (not shown), such as a toggle lever,whereby a first end of a first lever arm is connected to the outer tube110 and a first end of a second lever arm is connected to the inner tube120, and where second ends of the lever arms can be actuated by hand.This is, however, only an example, and any other mechanism fordisplacing and locking the tubes 110, 120 relative to each other canalso be implemented.

The outer tube 110 and the inner tube 120 each has a respective frontportion 111, 121. An outer surface of the front portion 111 of the outertube 110 may be slightly tapered towards a free end 110 a of the outertube 110. At least the front portion 121 of the inner tube 120 may beguided in the front portion 111 of the outer tube 110. A free end 120 aof the inner tube 120 may abut against a circumferentially extendingshoulder 111 a on an inner wall of the outer tube 110. Further, a recess112 is formed that extends from the free end 110 a of the outer tube110, and through the front portion 111 of the outer tube 110 and thefront portion 121 of the inner tube 120. The recess 112 has an innerdiameter or width that is at least as large as an outer diameter of thereceiving part 5 in the region of the rib-free surfaces 55 a, 55 b, suchthat the instrument 100 can be placed onto and around the receiving part5 and the clamping ring 8. A length of the recess 112 in an axialdirection is such that the receiving part 5 can be accommodated in thefront portion 111, 121 of the tubes 110, 120 of the instrument 100.Thus, the inserted rod 6 can also extend through the recess 112. At adistance from the free end 120 a of the inner tube 120, an innershoulder 122, for example an annular shoulder, is formed, which servesas an abutment for the first end 5 a of the receiving part 5, asdepicted in FIGS. 19 a and 20 a . By means of the recess 112, two freelegs are formed on the instrument 100. The shape of the recess 112 issuch that the width of the legs may decrease towards the free end 110 a.This facilitates easier finding of the receiving part 5 in-situ andplacing of the instrument 100 onto the receiving part 5 in-situ duringsurgery.

At a distance from the free end 110 a, the outer tube 110 definescircumferentially extending grooves 113 a, 113 b in an inner wall of thelegs, respectively. The number and shape of the grooves 113 a, 113 brespectively corresponds to the number and shape of the ribs 83 a, 83 bof the clamping ring 8. In the embodiment shown, two axially spacedapart grooves 113 a, 113 b are provided on each side. The grooves 113 a,113 b are configured to engage the ribs 83 a, 83 b of the clamping ring8. Similarly, circumferentially extending grooves 123 a, 123 b areprovided at an inner wall of the inner tube 120 at a distance from thefree end 120 a. The grooves 123 a, 123 b are configured to cooperatewith the ribs 54 a, 54 b of the receiving part 5. When the inner tube120 is at an engagement position of the instrument 100, described ingreater detail below, the distance between the grooves 113 a, 113 b ofthe outer tube 110 and the grooves 123 a, 123 b of the inner tube 120corresponds to the distance between the ribs 83 a, 83 b on the clampingring 8 and the ribs 54 a, 54 b on the receiving part 5 when the clampingring 8 is at the upper position as depicted in FIG. 18 a.

The instrument 100 as a whole, or parts thereof, may be made of one ormore of the same materials mentioned above with respect to the polyaxialbone anchoring device.

The operation of the instrument 100 is as follows. First, as illustratedin FIGS. 18 a to 18 c , the steps of placing the instrument 100 onto thereceiving part 5 are illustrated. In FIG. 18 a , the bone anchoringelement 1 may already be inserted into a bone. The clamping ring 8 is inthe upper position and the projections 85 engage the recesses 56 of theupper part 50 of the receiving part 5. The rod 6 and a fixation element9 may already be inserted in the receiving part 5, but the fixationelement 9 is not tightened so that the rod 6 is still movable along therod axis, and may also have some space for moving axially up and downrelative to the receiving part 5. The front portion of the instrument100 is oriented such that the legs of the instrument 100 are alignedwith the rib-free surface portion 55 a, 55 b of the receiving part 5 andthe rib-free surface portions 84 a, 84 b of the clamping ring 8. Then,as depicted in FIG. 18 b , the instrument 100 is moved downward relativeto the receiving part 5 so that the legs of the instrument 100 areplaced over the receiving part 5 until the first end 5 a of thereceiving part abuts against the inner shoulder 122 of the inner tube120 (depicted in FIGS. 19 a and 20 a ). In this position the grooves 113a, 113 b of the outer tube 110 are at a same axial position as the ribs83 a, 83 b of the clamping ring 8, and the inner grooves 123 a, 123 b ofthe inner tube 120 are at a same axial position as the ribs 54 a, 54 bof the receiving part 5. Therefore, when the instrument 100 is rotated,the grooves 113 a, 113 b of the outer tube 110 engage the ribs 83 a, 83b of the clamping ring 8, and at the same time, the grooves 123 a, 123 bof the inner tube 120 engage the ribs 54 a, 54 b of the receiving part5, as shown in FIG. 18 c.

The cooperation of the engagement structures in the form of ribs andgrooves connects the outer tube 110 to the clamping ring 8 and the innertube 120 to the receiving part 5 in form-fit manners, respectively, suchthat a force for moving the clamping ring 8 relative to the receivingpart 5 in an axial direction can be transmitted through the instrument100.

FIGS. 19 a to 20 b illustrate the use of the instrument 100 for bothlocking of the head 3 and releasing the lock on the head 3 relative tothe receiving part 5. In FIGS. 19 a and 19 b , the clamping ring 8 is inthe upper position, where the upper end 8 a abuts against a lower end 50a of the upper part 50 of the receiving part 5. The head 3 is pivotablein the head receiving portion 57, but cannot be pulled out through theopening at the lower end 5 b. The receiving part 5 is held by the innertube 120 in a form-fit manner, so that the receiving part 5 cannot moverelative to the inner tube 120, at least in an axial direction. Theclamping ring 8 is engaged by the outer tube 110. As can be seen in FIG.19 b the front end 120 a of the inner tube 120 abuts against theshoulder 111 a of the outer tube 110.

As can be seen further in the figures, an inner diameter of the innertube 120 above the shoulder 122 is such that the fixation element 9 canbe inserted through the inner tube 120 and into the upper part 50 of thereceiving part 5.

In the next step, as depicted in FIGS. 20 a and 20 b , the outer tube110 is moved downward relative to the inner tube 120, so that theclamping ring 8 is moved slightly downward relative to the receivingpart 5, thereby compressing head receiving portion 57. As depicted ingreater detail in FIG. 20 b , the clamping ring 8 has moved downwardaway from the abutment of the upper part 50 of the receiving part 5 andthe widening outer surface portion 57 a of the head receiving portion 57and the tapered inner surface portion 87 of the clamping ring 8cooperate to generate an increasing pressure in a radial direction ontothe head 3 and the pressure member 7. By means of this, the head 3 islocked in the receiving part 5 in its pivotal position by the instrument100 acting onto the clamping ring 8. Meanwhile, the rod 6 is stillmovable to allow adjustments of the rod position relative to thereceiving part 5. In this locking position of the clamping ring 8, asshown in FIGS. 20 a and 20 b , the instrument 100 can also be used topull the bone anchoring device towards the inserted rod 6, to correct aposition of the associated vertebra.

Next, for performing further adjustments, the lock on the head 3 can bereleased, where the outer tube 110 is pulled up relative to the innertube 120, until the shoulder 111 a abuts against the free end 120 a ofthe inner tube 120. Thereby, the clamping ring 8 is moved upward out ofthe locking position and back into the open position, which is the sameposition depicted in FIGS. 19 a and 19 b.

With the possibility of locking the head 3, and then also of releasingthe locked head 3, while the rod 6 and the fixation element 9 arealready inserted in the receiving part 5, a greater variety ofadjustment steps can be carried out, which simplifies the surgicalprocedure. For example, the polyaxial bone anchoring device togetherwith the instrument 100 can be used in a similar manner as a polyaxialbone anchoring device with a two part fixation element that providesindependent rod and head fixation, wherein, for example, an innerfixation element is used to fix the rod and an outer fixation element isused to lock the head independently from the locking of the rod.

In another manner of use, the polyaxial bone anchoring device can beused as a monoaxial bone anchoring device, in that the head 3 is lockedrelative to the receiving part 5 while adjustments to the rod positionscan still be made.

As depicted in FIG. 21 a , in the locking position of the clamping ring8, the bone anchoring device can be pulled against the rod and theposition of the vertebra can be corrected. Finally, as shown in FIG. 21b , once a correct angular position of the head 3 and a correct positionof the receiving part 5 relative to the rod 6 has been found, thefixation element 9 can be tightened, for example, with a drive tool 300that is inserted through the inner tube 120 and that engages thefixation element 9. Tightening of the fixation element 9 moves the rod 6downwards, which in turn presses the rod 6 onto the rod support surface78 of the pressure member 7 and locks the whole device. The instrument100 can then be removed by rotating the instrument 100 so that thegrooves 113 a, 113 b, 123 a, 123 b disengage from the ribs 83 a, 83 b,54 a, 54 b and the legs of the instrument 100 are aligned with therib-free surfaces 55 a, 55 b, 84 a, 84 b. In this position, theinstrument 100 can be pulled away from the receiving part 5. Theextended tabs at the first end 5 a of the receiving part 5 may then bebroken off at the end of the procedure.

In a surgical operation, a plurality of bone anchoring devices areconnected by the rod 6. It may be possible to use several instruments100, respectively, for several bone anchoring devices simultaneously,which facilitates the steps such as the adjustment, re-positioning, etc.of each bone anchoring device relative to the rod 6.

A further embodiment of a bone anchoring device and instrument is shownwith respect to FIGS. 22 and 23 . The embodiment according to FIGS. 22and 23 differs from the previous embodiments only in the engagementstructures for the instrument and the bone anchoring device. All otherparts are the same or similar to the previously described embodiments,and are indicated with the same reference numerals as in the previousembodiments, and their descriptions therefore will not be repeated. Thereceiving part 5′ has grooves 154 a, 154 b at an outer wall of each ofthe legs 52 a, 52 b. The circumferentially extending grooves 154 a, 154b are located at a distance from the groove 5 c that provides thebreak-off section. The instrument 100′ has corresponding circumferentialribs 133 a, 133 b at an inner wall of the inner tube 120. The ribs 133a, 133 b are at a position and are shaped so as to be able to engage thegrooves 154 a, 154 b of the receiving part 5′. The function andoperation of the parts may be the same as similar to that of thepreviously described embodiments. For engaging the receiving part 5′with the instrument 100′, the legs of the instrument 100′ have to bespread when placing the instrument 100′ over the receiving part 5′.

A further modified embodiment of the instrument, which facilitateseasier outward splaying of the legs is depicted in FIG. 24 . Likenumerals denote the same or similar parts as in the previousembodiments. In the instrument 100″ shown in FIG. 24 , the outer tube110 and the inner tube 120 are both provided with slots 200 a, 200 b,which allow the legs to spread apart more easily when the instrument100″ is moved downward relative to the bone anchoring device, similarlyas shown in FIGS. 18 b and 18 c . The circumferential ribs 133 a, 133 bmay thus more easily slide over the outer surface of the receiving part5′ and snap into or otherwise engage the corresponding grooves 154 a,154 b. Depending on the particular design of the instrument 100″ and/orthe bone anchoring device, a further rotation step for engaging therespective parts may or may not be necessary.

Further modifications can also be contemplated. For example, on each ofthe receiving part and/or the clamping ring, any different combinationof ribs and grooves can be provided, and the instrument may have acounterpart or complementary structure, in other words, a combination ofgrooves and ribs configured to engage the structures at the receivingpart. The shape and the number of the engagement elements may also vary.One single engagement element on the receiving part and the clampingring may be sufficient in some embodiments. The ribs and grooves neednot extend circumferentially in a plane in some embodiments, but caninstead extend along a helix-shape, for example. Therefore, theengagement structures on the instrument, the receiving part, and theclamping ring can also be realized with, for example, threads. Otherengagement structures may also be contemplated that provide a form-fitconnection which can transmit forces onto the bone anchoring device andwhich can be affected by a rotating and/or sliding movement of theinstrument relative to the bone anchoring device. In some embodiments,the engagement structures may also be provided on only one side of thereceiving part and on one side of the clamping ring. The position of theengagement structures may be different from that shown in theembodiments above.

The bone anchoring device according to other embodiments of theinvention can be provided in still further modified forms. For example,the head of the bone anchoring element can have any other shape, suchas, for example, a cylindrical shape, or a spherical shape withflattened sides, wherein a monoplanar device is provided that allowspivoting of the bone anchoring element in a single plane. The head canalso be conically shaped or otherwise shaped, where the internal hollowsection of the head receiving portion can be adapted to the specificshape. In a further modification, the flexibility of the head receivingportion may be based on or facilitated by properties of the material,for example, a plastic material may be used, and the slits in the headreceiving portion may be fully or partly omitted.

In the pressure member, the upstanding legs may be omitted. Otherstructures may be provided that prevent the pressure member fromescaping out of the receiving part during insertion of the head. Thepressure member may also be shaped such that it can be inserted from thelower end of the receiving part.

In some embodiments, the head receiving portion can have an inclinedopen end or can be otherwise asymmetric to allow for a greaterangulation of an inserted head in one direction.

The outer surface of the head receiving portion and the inner surface ofthe clamping ring can also have various other shapes that result incompression of the head receiving portion by the clamping ring when theclamping ring is shifted downward. Also, the clamping ring can havevarious other designs.

The alignment features such as the flat portions can have any othershape or can be omitted. Only one alignment feature may be provided insome embodiments. The projections and the recesses for securing therotational position of the clamping ring relative to the receiving partcan also have any other shape. There can be more or less than oneprojection or recess. The recess may be present at the clamping ring andthe projection at the receiving part. The rotational securing structurecan also be omitted.

The extended tabs on the receiving part can be omitted. In addition, insome embodiments, other kinds of fixation elements can also be used, forexample, non-threaded locking elements that have an alternativeadvancement structure. In addition, all kinds of bone anchoring devicescan be used, such as, for example, nails or bone anchors with barbs.

Meanwhile, the use of the instrument has been shown in connection with abone anchoring element that has already been inserted into the bone. Thebone anchoring element may also be pre-assembled with the receivingpart. In this case, the bone anchoring device can be a top-loadingpolyaxial bone anchoring device in some embodiments.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, but is instead intended tocover various modifications and equivalent arrangements included withinthe spirit and scope of the appended claims, and equivalents thereof.

1. A bone anchoring device comprising: a receiving part for coupling arod to a bone anchoring element, the receiving part comprising a firstend, a second end below the first end, a central axis extending betweenthe first end and the second end, a recess at the first end forreceiving the rod, and a head receiving portion at the second end forpivotably holding a head of the bone anchoring element; and a clampingring positionable around the head receiving portion, wherein when theclamping ring is around the head receiving portion, the clamping ring ismovable from a first position wherein an inserted head is pivotablerelative to the receiving part, to a second position wherein theclamping ring exerts a radial force onto the head receiving portion tolock the inserted head relative to the receiving part; wherein when theclamping ring is at the first position, a portion of the clamping ringabuts a portion of the receiving part to restrict movement of theclamping ring towards the first end of the receiving part.
 2. The boneanchoring device of claim 1, wherein the receiving part comprises afirst engagement structure and the clamping ring comprises a secondengagement structure respectively configured to be engaged by theinstrument to transmit a force via the instrument onto the clamping ringand onto the receiving part, such that the clamping ring and thereceiving part can be moved relative to each other along the centralaxis.
 3. The bone anchoring device of claim 2, wherein the firstengagement structure and the second engagement structure are arranged atan outer circumferential surface of the receiving part and the clampingring, respectively.
 4. The bone anchoring device of claim 3, wherein thefirst engagement structure extends farther radially outwardly than allother portions of the receiving part.
 5. The bone anchoring device ofclaim 3, wherein the second engagement structure extends fartherradially outwardly than all other portions of the clamping ring.
 6. Thebone anchoring device of claim 2, wherein the first engagement structureis arranged at a distance from the first end of the receiving part. 7.The bone anchoring device of claim 2, wherein the first engagementstructure and the second engagement structure is each arrangedasymmetric with respect to a plane extending through the central axis ofthe receiving part and through a longitudinal axis of the recess.
 8. Thebone anchoring device of claim 2, wherein the first engagement structureand the second engagement structure are engageable with the instrumentthrough rotating the instrument around the central axis.
 9. The boneanchoring device of claim 2, wherein the first engagement structure andthe second engagement structure each comprises at least onecircumferentially extending rib or at least one circumferentiallyextending groove.
 10. The bone anchoring device of claim 1, wherein thehead receiving portion comprises a tapered outer surface portion. 11.The bone anchoring device of claim 10, wherein the clamping ringcomprises a tapered inner surface portion that cooperates with thetapered outer surface portion of the head receiving portion.
 12. Thebone anchoring device of claim 1, wherein the head receiving portioncomprises a narrowing inner surface portion at the second end. 13.(canceled)
 14. The bone anchoring device of claim 1, wherein when theclamping ring is around the head receiving portion, the clamping ring issecured against rotation relative to the receiving part. 15-16.(canceled)
 17. A bone anchoring device comprising: a bone anchoringelement comprising a shank for anchoring to bone and a head; a receivingpart for coupling a rod to the bone anchoring element, the receivingpart comprising a first end, a second end, a central axis extendingbetween the first end and the second end, a recess at the first end forreceiving the rod, and a head receiving portion at the second end forpivotably holding the head; and a clamping ring positionable around thehead receiving portion; wherein when the clamping ring is around thehead receiving portion, the head is insertable into the head receivingportion, and the clamping ring is movable from a first position whereinthe inserted head is pivotable relative to the receiving part, to asecond position wherein the clamping ring exerts a radial force onto thehead receiving portion to lock the inserted head relative to thereceiving part.
 18. The bone anchoring device of claim 17, wherein thehead of the bone anchoring element is insertable into the receiving partfrom the second end. 19-22. (canceled)